During mitosis in vertebrate cells the chromosomes are pushed away from the spindle poles by a "polar ejection force". It is currently unclear whether this force is generated by the growing ends of polar microtubules that impact the chromosomes, or by microtubule-based molecular motors that decorate the surface of the chromosome, which then interact with microtubules growing from the poles. To distinghish between these models wer are microinjecting newt lung cells with AMP/PMP which inhibits microtubule-based motor activity but not microtubule growth. These cells are then transferred to the BMIRR's laser microsurgery/optical trapping LM where chromosome arms can be severed and analyzed. Once severed the arms can also be optically trapped to estimate the forces genereated by the ejection field.